diff options
Diffstat (limited to 'contrib/ltree/ltree_op.c')
| -rw-r--r-- | contrib/ltree/ltree_op.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/contrib/ltree/ltree_op.c b/contrib/ltree/ltree_op.c index be2733273f..3eb854fbdc 100644 --- a/contrib/ltree/ltree_op.c +++ b/contrib/ltree/ltree_op.c @@ -1,7 +1,7 @@ /* * op function for ltree * Teodor Sigaev <teodor@stack.net> - * $PostgreSQL: pgsql/contrib/ltree/ltree_op.c,v 1.16 2007/02/28 22:44:38 tgl Exp $ + * $PostgreSQL: pgsql/contrib/ltree/ltree_op.c,v 1.17 2008/03/09 00:32:09 tgl Exp $ */ #include "ltree.h" @@ -609,6 +609,7 @@ ltreeparentsel(PG_FUNCTION_ARGS) double mcvsum; double mcvsel; double nullfrac; + int hist_size; fmgr_info(get_opcode(operator), &contproc); @@ -626,21 +627,31 @@ ltreeparentsel(PG_FUNCTION_ARGS) */ selec = histogram_selectivity(&vardata, &contproc, constval, varonleft, - 100, 1); + 10, 1, &hist_size); if (selec < 0) { /* Nope, fall back on default */ selec = DEFAULT_PARENT_SEL; } - else + else if (hist_size < 100) { - /* Yes, but don't believe extremely small or large estimates. */ - if (selec < 0.0001) - selec = 0.0001; - else if (selec > 0.9999) - selec = 0.9999; + /* + * For histogram sizes from 10 to 100, we combine the + * histogram and default selectivities, putting increasingly + * more trust in the histogram for larger sizes. + */ + double hist_weight = hist_size / 100.0; + + selec = selec * hist_weight + + DEFAULT_PARENT_SEL * (1.0 - hist_weight); } + /* In any case, don't believe extremely small or large estimates. */ + if (selec < 0.0001) + selec = 0.0001; + else if (selec > 0.9999) + selec = 0.9999; + if (HeapTupleIsValid(vardata.statsTuple)) nullfrac = ((Form_pg_statistic) GETSTRUCT(vardata.statsTuple))->stanullfrac; else |